im going from 16 by 8s to 17 by 9.5" ZR1's...do i need to get any spacers or anything to get ehse to fit. I knwo i gotta get my comp reporgrammed for the diff size and all...thanks.

 

no spacers neccesary, and a comp reprogramming isnt neccesary either

 

but then my speedo will be off won't it?

 

not much, if at all

 

no it wont be off at all really if you go with a 275/40/17 tire because they are similar to the 245/50/16. i forget what word i want to say they are the same, diameter?
But no spacers needed and no comp. reprgramming.
Ive already looked into that before when i got mine.
Check out my wheels if ya want!~>in the sig.
do a search on the computer reprogram, and you'll find out why you dont need it done

 

PCM doesn't need to be programmed because they are the same height with wheels and tires. The 275/40/ is thinner then the regular 245/50 is it? So the extra inch in the wheel makes up for it. Basically the are the same height.

 

In going from a 245/50R16 to a 275/40R17....

When your speedo says 65 MPH, you're going 65.03.

Negligible difference.

 

that is fantastic...chris, i'll be ordering tires from ya soon ( and maybe 2 silver Zr1s if i cant find any used)

 

You do need to select the correct offset for the 17x9.5" ZR1's. The offset preferred by most is the 56mm one. There is also a 38mm offset, which puts the outer edge of the tire a little too close to the outer edge of the front fender for some people, and may result in some rubbing at full lock.

One thing people forget when looking at the outer diameter of the tires is that not all Z28's came from the factory with 245/50-16 tires (25.7"). You only got those if the car was ordered with the Z-rated tire package, RPO code "QLC". If you didn't get the QLC package, the car came with 235/55-16 tires that are 26.1-26.2" outside diameter.

 

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I just went from 255X50X16 to 275X40X17 will there be speedo change?

Thanks in advance

Bruce/StoreKeeper99Z28

 

You've decreased the diameter by 1.5%. Your speedo will be reading 61mph, instead of 60mph. But, whether the speedometer is right or wrong will depend on what size tires came on you car from the factory, and whether you made any changes to the PCM for the 255's. Its no big deal in either case.